The realisation of complex integrated devices requires efficient electrical separation between various sections of the device.
Current solutions to provide separation regions rely on proton implantation or introduction of defects (such as hydrogen complexes) by dry etching techniques, thus converting the original p- or n-type conduction material to semi-insulating. A further alternative solution lies in the partial removal of the upper cladding layer such as to obtain a restricted channel for carrier conduction.
Defect creation by proton implantation is a technique not easily accessible for production, while defects originated by dry-etching techniques tend to be partially eliminated by heat treatments. This also gives rise to concerns in terms of degradation of performance over time especially in the case of devices having high operating temperatures.
Patent documents generally exemplary of some of the techniques considered in the foregoing are US-B-6 597 718, EP-B-0 672 932 and US-A-2004/0084683.
Specifically, US-B-6 597 718 is exemplary of insulation obtained by the conventional method of reducing the upper cladding thickness to increase electrical separation. This document specifically refers to the integration of a Fabry-Perot laser with an EAM modulator.
EP-A-0 672 932 is exemplary of butt-joint passive region in which electrical insulation is obtained by proton implantation or iron doping.
US-A-2004/0084683 is exemplary of a technique based on the partial removal of the upper cladding layer, wherein electrical separation is achieved again via proton implantation or iron doping.
FIG. 1 of the annexed drawing is exemplary of a conventional prior art arrangement including a semi-insulating (SI) region between the sections to be separated. This arrangement includes two device sections A and B. While these sections may be of any known type, in the specific arrangement illustrated in FIG. 1, the section A has grown thereon a distributed feedback (DFB) grating. Both sections A and B have associated an upper cladding and contact layer 14 (typically of the p-type).
Reference numeral 16 designates a semi-insulating (SI) material provided as a separation between the sections A and B. Typical examples for semi-insulating materials for the region 16 are InP:Fe or InGaAsP.
Essentially, the principle of operation of semi-insulating region 16 as shown in FIG. 1 (which is typically grown after removal of the upper doped cladding) is related to that region being doped with elements providing deep acceptor traps, as for example InP:Fe. A disadvantage of this solution lies in that iron doped materials are effective in blocking electrons but have limited effects on holes.
The foregoing description of prior art arrangements clearly indicates that the need exists for techniques that may provide an improved electrical separation in integrated devices, especially as regards integrated optoelectronic devices.
The purpose the present disclosure is thus to provide such an improved solution.